Help. Is this postpartum depression??

I’m 22 and a single mother. After 5 years of dealing with a toxic relationship, i finally said goodbye to my children’s father and he doesn’t do anything (doesn’t see them or help support). My son will be 3 in May, and my daughter is currently 4 months old. When i had my son, i was so attached to him. I loved him so much i felt like my heart was going to explode. And i felt this way up until i gave birth to my daughter. Of course I love him to death, but i just feel disconnected i guess you could say. And i feel the same with my daughter. I think they’re both the best, cutest, kids in the world and i love them with all my heart. I just feel like something is off. At first i felt like i was just having a hard time adjusting to having two kids, but it never went away. I feel like an awful mother admitting this. I never spoke about this to anyone bc of how it sounds. But if its something i can fix, i want to do this ASAP. I feel like I’m missing out on their lives just bc i feel distant from them.

Could this be postpartum depression? I’ve struggled with depression in high school, but I’ve been doing great until now. I don’t necessarily feel sad or anything, but i don’t know what else this could be :(((